Brian Cookson, the NASUWT's national treasurer, called on the conference to support a campaign of industrial action - up to and including strikes - against a range of government policies.

He told the conference that "education is on the front line facing this attack" on the public sector - and called on them to back a motion which brought together concerns about pay, teachers' rights and "safeguarding state education".

Mr Cookson said the calls for "school autonomy disguised the true aim of academy chains taking over vast numbers of schools, replacing the democratically accountable local authority system".

'Intimidation and lies'

The motion supported by the conference said that the teaching profession faced "scurrilous attacks, abuse, intimidation and lies".

Derek Moore, the NASUWT executive member for Greater London, said the expansion of academies was about making the education system accessible to "privateers".

Anne Brimacombe, executive member for the West Midlands, warned against schools being forced to become academies - and said that this "predatory privatisation should be brought out into the open".

The government was behaving as if it were "at war" with the teaching profession, said deputy head teacher Martin McCusker, who said that education and health remained the last major targets for those wanting to reduce the public sector.

There were also criticisms of school watchdog Ofsted, with accusations that it was undermining and "deprofessionalising" teachers.

The proposals backed by the conference will allow the union's leadership to carry out a flexible campaign in the autumn, with actions short of striking as well as opening the way for a ballot for strikes.

The NASUWT's conference vote for a campaign of industrial action is a UK-wide decision - but the union can run local, regional and national campaigns.

Education policies are devolved, which also means there can be different teachers' union campaigns in England, Scotland, Wales and Northern Ireland.

"Teachers do not feel there is any area of their working lives the government has not trampled over and it is impairing their ability to focus on raising standards for pupils," said Chris Keates, the union's general secretary, speaking ahead of the debate.

'Putting children first'

Speaking to the BBC News Channel following the vote, Mr Cookson added: "We have a world class education system - that is something we must protect for future generations. What the government is always talking about is destroying that state education system that is so vital to us."

He said members were "absolutely frustrated" at the way they were being treated, and the appetite for industrial action "was building".

It was not an appetite teachers relished, he said, adding "teachers want to teach, they want to do their very best for pupils".

A Department for Education spokesman said: "It is absurd to say our school reforms are a 'vicious assault' on the teaching profession. They are all about putting children first and raising standards.

"We have given teachers more powers to tackle bad behaviour in the classroom and have introduced new laws to protect them from malicious allegations. We've also allowed schools to run their own affairs by becoming Academies, and we have slashed bureaucratic paperwork to free-up teachers' time.

"We are putting power back into the hands of talented heads and teachers - allowing them to get on with raising standards without interference from Whitehall or politicians.